The invention relates to a compressor system for supplying compressed air in a commercial vehicle, having a compressor, a clutch and a hydraulic pump, with it being possible for the compressor system to be driven via a drivetrain and for the compressor to be completely decoupled from a drive engine by use of the clutch.
The invention also relates to a method for operating a compressor system for supplying compressed air in a commercial vehicle, having a compressor, a clutch and a hydraulic pump, with the compressor system being driven via a drivetrain and with the compressor being completely decoupled from the drive engine by use of the clutch.
Modern commercial vehicles have numerous subsystems which are operated with compressed air. These include, for example, a compressed-air-operated service brake or an air suspension system. To ensure the supply of compressed air to these subsystems, a compressed air supply device which includes a compressor is normally provided in the commercial vehicle. The compressor is driven mechanically by an engine of the commercial vehicle. The coupling of the compressor normally takes place by means of a toothing on one end of the crankshaft of the drive engine. The compressor itself has a further crankshaft, with a hydraulic pump, for example a power steering pump, often being arranged on the side of the further crankshaft which faces away from the drive-side toothing. The hydraulic pump is connected to the shaft of the compressor by way of a radial-play compensating bearing, for example a Maltese cross, or a multitooth bearing which can withstand a higher torque, but tolerates a smaller degree of play, than the Maltese cross.
Furthermore, in modern commercial vehicles, a clutch is often provided, which is capable of completely decoupling the compressor from the drive engine in order to save energy. In the conventional arrangement of the hydraulic pump on the drive output side of the crankshaft of the compressor, this means that the hydraulic pump is also decoupled from the drive at the same time as the compressor. However, this has the result that, for example, steering assistance in the form of a power steering system for the vehicle would no longer be available. This cannot be tolerated for safety reasons.
Various alternatives are known for solving this problem. One option is to reduce the action of the steering assistance when the compressor is shut down. In this variant, it is assumed that the compressor can be decoupled primarily on motorways. On such roads, on account of the small radii of the curves, the steering assistance is also not absolutely necessary. However, if a steering maneuver must be carried out, for example for collision avoidance, the steering assistance is not available and the compressor would have to be activated.
A further option is for the steering assistance to be provided purely electrically. A power steering pump which is driven mechanically by the drive engine is then no longer provided, and the pump requires a separate electric motor. This can be realized in principle, but the electric motor must be capable of generating a high power of approximately 50 kW, and it therefore also takes up a corresponding amount of space and weight. Furthermore, the energy consumption is less expedient.
It is therefore an object of the present invention to improve upon a compressor system such that a complete decoupling of the compressor from the drive engine with simultaneous operation of the hydraulic pump is possible without a large amount of excess mechanical expenditure.
This and other objects are achieved by a compressor system for supplying compressed air in a commercial vehicle, having a compressor, a clutch and a hydraulic pump, with it being possible for the compressor system to be driven via a drivetrain and for the compressor to be completely decoupled from a drive engine by way of the clutch. The drivetrain includes a gear drive via which the hydraulic pump can be driven. The clutch is arranged between the gear drive and the compressor.
Here, the arrangement of the clutch between the gear drive and the compressor is not to be understood to mean that the clutch is positioned spatially between the gear drive and the compressor. The expression “between” rather describes the path of the transmitted force. The force is transmitted from the gear drive via the clutch to the compressor. It is, however, contemplated for the clutch to also be arranged spatially between the gear drive and the compressor on account of structural requirements. As a result of the arrangement of the clutch between the gear drive and the compressor, decoupling of the compressor from the drive engine is possible without adversely affecting the drive of the hydraulic pump. Here, the only additional mechanical component required is the gear drive in the drivetrain, via which gear drive a power take-off is provided for the hydraulic pump. Furthermore, the mechanical connection of the compressor system to the drive engine may remain unchanged in relation to a conventional compressor system.
Here, it is preferably provided that the compressor and the hydraulic pump are integrated in a common housing. The accommodation of the compressor and hydraulic pump in a common housing facilitates the cooling of both components, because a common cooling system can be used. For example, the common housing can be cooled overall in a simple manner.
It is particularly preferable for the gear drive to have a transmission ratio not equal to one. By providing a transmission ratio not equal to one in the gear drive, the compressor and the hydraulic pump can be operated at different rotational speeds. This enables a separate optimization of the compressor and hydraulic pump for the vehicle.
It is also advantageous for the compressor system to include a further drive on that side of the compressor which faces away from the gear drive. By providing a further drive on that side of the compressor which faces away from the gear drive, a mechanically more stable construction is made possible. The further drive may, for example, be designed as a further gear drive, as a belt drive or as a chain drive. Furthermore, on that side of the compressor which faces away from the gear drive, a connection facility for the hydraulic pump is provided which is not restricted by the compressor in terms of the available installation space. In this design, a second connection facility may also be provided which may be used for connecting a further auxiliary unit, for example a coolant pump.
It may be provided that the gear drive is mounted partially by way of a bush, and that the bush simultaneously serves to mount a crankshaft of the compressor. The gearwheels used in the gear drive are conventionally rotatably mounted, wherein the simultaneous use of a bearing point of a gearwheel of the gear drive for mounting the crankshaft simplifies the mechanical design of the compressor system.
Here, it is provided in particular that the gear drive and the crankshaft are coupled to one another in a freely rotatable manner by way of the bush. The freely rotating coupling between the gear drive and the crankshaft makes the shut-down of the compressor by way of the clutch possible for the first time.
A method for operating a compressor system is improved in that the hydraulic pump is driven by the drivetrain via a gear drive, and in that the drivetrain is separated between the gear drive and the compressor in order to decouple the compressor from the drive engine. In this way, the advantages of the compressor system according to the invention are also realized within the context of a method. This also applies to the particularly preferred embodiments of the method according to the invention specified below.
The method is expediently refined in that the compressor and the hydraulic pump are integrated in a common housing. It is preferably provided here that the hydraulic pump is driven via the gear drive with a transmission ratio not equal to one. And, it is particularly preferable for the compressor to be driven via a further drive which is arranged behind the gear drive as viewed from the drivetrain.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.